Sometimes I wonder if you guys know what you're talking about when it comes to springs, shocks and struts.
There is nothing wrong with the C springs, B springs, bullit springs, or the Mach1 springs. There are differences between all 4, some differences smaller than others.
In general, if you're into handling, you're going to want linear rate springs. If you want a soft ride, you want some progressive rate springs. On the other hand, mismatched shocks/struts and springs will give you a bad ride no matter what. Also, linear rate springs do not = bad ride!!!
Linear rate: This means that the spring rate is constant no matter how compressed the spring is.
Progressive rate: This means that the spring rate increases as the spring is compressed. This will give a slightly better ride, but it's going to be hard to find a cheap shock/strut combo that can dampen the spring constantly throughout its compression. Therefore, if you buy a shock/strut combo for a linear rate spring and put it on with a progressive rate spring, it's going to handle like crap because the spring doesn't spend much time at that one spring rate. Essentially, they can't control the suspension's movement and therefore you get a bouncy or sloppy ride!
I wouldn't buy Eibach springs unless I knew I could find shocks/struts that will work with those spring rates. Furthermore, I would never buy any springs that I couldn't find out what the rates were for them.
To sum it all up, there is nothing wrong with the Bullitt or Mach1 kits. They aren't cheap because they're crappy, they're cheap because they are surplus!!
I'm tired of typing...

If anyone has any questions, just drop me a PM, I'd love to help anyone out!